With a background in mechanical engineering, I have a real fascination for ram pumps. With no other visible energy inputs, they can appear to be perpetual motion machines until you understand what is going on below the surface. Their simplicity of design is genius, and they are real mechanical works of art. These pumps deliver water continually with no electricity or other added energy, and very minimal maintenance.
A ram pump uses the downhill flow of water to pump a portion of it uphill. You can pump up to 25 percent of your supply water, depending on the drop and the lift. Ram pumps will work on sites with 3 to 50 feet (0.9–15 m) of head (vertical drop) and can deliver to elevated sites far from the pump and source.
Ram pumps are quite efficient for a mechanical pump—more than 75 percent in many cases. Efficiency is calculated by multiplying the amount of water delivered by the delivery height, and then dividing by the amount of water consumed times the input head. And with enough head and flow, ram pumps can deliver thousands of gallons per day up to 500 feet above the pump site. The output of a ram pump system can be estimated by this formula:
Water Delivered = Available Water x Source Fall x 0.5 ÷ Delivery Height
The price range for a new pump is US$250 to $1,700, depending on size, materials used, and durability. When including steel drive pipe, metal ball valves, and other quality components, the price can appear high. But you will end up with a system that will last for decades. Some of the less expensive pumps are plastic, and designed to work at low head and flow. They are not able to take the incessant beating of the “hammer effect” that many ram pump installations will dole out to the pump and drive pipe fittings.
Five different ram pump sizes are available from Rife Hydraulic Engine Manufacturing Company. Other excellent pumps are on the market, including Folk brand ram pumps, which have a slightly different design, and use durable, space-age materials in the valves. (See HP40 for a Folk ram pump installation article.)
A ram pump usually involves more work to set up than a motorized pump, but is extremely reliable and tough. I’m pretty sure they will outlast any electric pump you would choose to compare them to, and a solar-direct-powered pump could never match their 24-hour-a-day availability.